This invention relates to safety systems for protecting vehicular passengers, such as those traveling in automobiles and aircraft, and more particularly to those safety systems which utilize passive restraints, such as air bags and similar inflatable restraints which require almost instantaneous inflation from gas sources, such as compressed air or the reaction products of pyrotechnic inflator cartridges.
Inflatable gas cushions (air bags) are widely used in certain types of passenger carrying vehicles, most prevalently in land based automotive equipment. Generally, passive passenger restraints, such as inflatable gas bags are filled by compressed air or other gases and are located in the automobile steering column and in other fixed locations within the automobile, such as the dashboard and side panels. In the event of sudden deceleration of the vehicle, as in a crash, sensors identify the event and the compressed air or other gas is released to expand the bags at high speed directly towards the passenger. Air bags have generally proven to be effective in alleviating to some extent injuries which might otherwise be occasioned by virtue of a passenger striking a rigid surface within the vehicle. On the other hand it has now become apparent through experience that in some instances occupants require protection from the rapid inflation of the aribag system itself.
It has in the past been proposed, for various reasons, to inflate the protective air or gas filled cushion gradually, usually by sequentially releasing inflating gas, so that the full force of deployment of the bag was extended over a longer period of time. Control of the rate of bag inflation might be desired for example, in response to the position of the vehicle occupant to be restrained, or as a function of the ambient temperature or even as a function of the severity of the impending crash event.
U.S. Pat. No. 5,460,405 which was issued Oct. 24, 1995 discloses a passenger protective inflating system in which an inflator assembly 20 is provided which contains a plurality of inflating gas sources 22, 24, 26 and 28 that are capable of supplying different volumes of gas, depending upon the instructions issued by controller 50. These four sources of inflating gas may be activated either simultaneously or in sequence depending upon the values received by controller 50 from sensors 52, 72 and 70.
A different type of multi-stage gas inflating apparatus is the subject of U.S. Pat. No. 3,972,545 which, in this case, discloses the use of separate quantities of ignitable materials contained within chambers 16 and 17 that are separated by a consumable partition 15. The reaction of combustible materials within chambers 16 and 17 are initiated by means of squibs 19 and 20 which can be fired either separately or simultaneously, depending upon the severity of the emergency situation that has been sensed.
When utilizing multiple sources of inflating gas, for example separate containers of compressed air, in which the gases are expanded and released suddenly in pulsed sequence into a common duct which flows the gas toward the cushion, a reverse pressure shockwave often results from the activation or firing of the first container of gas; this shockwave is then responsible for the premature activation or firing of the second or subsequent additional containers. Since sequential activation is undertaken to alleviate the severity of cushion expansion, the essentially simultaneous activation of all gas sources by the shock wave vitiates the original reason for sequential gas release.